Two experiments were designed to optimize pellet quality and to evaluate the effects of feeding broilers with different feed physical quality on their performance and gastrointestinal changes. In the first experiment, the Taguchi method was applied to optimize the pellet quality by changing four factors of particle size (3, 4 and 5, sieve size) adding water to the mixer (0, 10 and 20 liters/ton of feed), different oil sources (vegetable oil, a mixture of vegetable oil and fat powder, and fat powder) and adding pellet binder (0, 2 and 4 kg/ton of feed). Nine diets were selected from 81 combinations by Taguchi design of experiment and consequently pelleted throughout feed meal. The pellet samples were evaluated for pellet durability index (PDI). Our results showed that the best pellet quality was achieved by reducing the particle size of feed ingredient, by adding 4 kg binder, adding 20 liters of water per ton of feed in the mixer and using equal proportions of fat powder and oil. In the second experiment 1248 day-old chicks were used in a completely randomized design to test 8 different feed physical form with 6 replications (3 replicates male and 3 replicates female) of 26 birds each. The test groups were; diets containing 100% pellets without fine, 80% pellets and 20% fine, 60% pellets and 40% fine, 40% pellets and 60% fine, 20% pellets and 80% fine, 100% fine, crumble and mash. To produce the treatments for this experiment, first all the pellet and crumble feed was sieved and their fine was completely separated. Then, to produce fine, a part of the pellet was milled and mixed with pellets in certain proportions. Average daily feed intake, average daily weight gain, and feed conversion ratio and Coefficient of Variation of weight in the starter, grower, finisher, and total period were measured and calculated separately for male and female chickens. On the last day of the rearing period, 2 male chickens were randomly selected from each replicate, weighed, and slaughtered. Length and weight (relative live body weight) of intestinal and cecum, population of Lactobacillus and Escherichia coli , carcass yield, and short-chain fatty acids of the ileum were examined. The results showed that in general in both sexes with increasing the amount of fine, feed consumption, and final weight decreased (P 0.01), and the highest weight was related to the two treatments consuming 100% pellets and crumble. The results show that the highest daily weight gain is achieved with pellet feed up to 60% of fine and crumble and no significant difference was observed between pellet feed and crumble. The highest (P 0.01) feed conversion ratio was observed in the mash treatment. The effect of feed form and fine percentage on the population of Lactobacillus and Escherichia coli in the ileum area of ??male broilers showed that the lowest (P 0.05) population of Lactobacillus was related to the treatment contained 40% pellets and 60% fine. Also, the number of Escherichia coli bacteria was not affected by the treatments. The weight of gizzard at 41 days of age in chickens that used mash feed was significantly higher than other treatments (P 0.01).Overall findings of experiment 2 indicate that processing of feed ingredients and the high pellet durability index (low fine content) improve broiler performance. So that the pelletizing processes improved the yield compared to the fine feed up to 40% of the fine. Keywords: Broiler, Fe e d form, Pellet Quality, Taguchi, Performance, PDI.